1. Field of the Invention
The present invention relates to a method of controlling a terminal crimping device which produces terminal-equipped cables constituting a wire harness, or the like.
2. Description of the Prior Art
The terminal crimping device is, in general, composed of a crimper and an anvil set opposite to said crimper wherein the crimper performs the work of crimping terminals to the exposed conductors of cables through elevating actions thereof. In this connection, Japanese Laid-Open Patent Appln. No. 8-236,253 discloses that the elevating actions of the crimper are achieved by decelerating the rotation of the servo motor before being transmitted to a disk where the disk rotation is converted into a linear motion such that a ram carried by said crimper is elevated and lowered. A detailed explanation thereof will be given with reference to FIG. 10 and FIG. 11.
FIGS. 10A through 10C are figures explaining the action of the terminal crimping device; FIG. 11A is a graph showing the relationship between the crimper action time and the elevating speed; and FIG. 11B is a graph showing the relationship between the time and the motor current value wherein 1, 2, 3 in FIGS. 11A and 11B correspond to A, B and C in FIG. 10.
Referring to FIG. 10, the disk 7 is secured to the output shaft of the decelerator (not shown), which functions to decelerate the rotation of the servo motor.
The disk 7 secured at an axis thereof to the output shaft of the decelerator carries an eccentric pin (crank shaft) 8 thereon. A crank rod 9 is pivotally attached at an upper end thereof to the eccentric pin 8 while the crank rod 9 is pivotally attached at a lower end thereof to a ram 11. The ram 11 is movable slidably in a vertical direction within a ram guide which is provided within the inner surfaces of a frame (not shown)., In this way, the disk 7, the crank rod 9, the ram 11 and the ram guide constitute a piston/crank mechanism.
The ram 11 is formed at a lower end thereof with an engagement recess 13, which is removably loaded with an engagement head 16 of a crimper holder 15 carrying a crimper 14. Immediately beneath the crimper 14, an anvil 17 is secured to a base 2 positioned opposite to said crimper 14.
FIG. 10A shows the start of the crimping step in which the crank pin 8 of the disk 7 takes an uppermost position to place the crimper 14 at the top dead center position, wherein the descending speed of the crimper 14 stands at 0 while the load current stands at 0 as shown in FIG. 11A.
FIG. 10B shows a rotation of the disk 7 in the arrow-marked direction which causes the crank pin 8 to move downward until the crimper 14 reaches a position in its high speed descent to contact the barrel c of a terminal, thus starting a crimping action therefor. The descending speed of the crimper 14 is reduced before the contact thereof while reducing the load current.
FIG. 10C shows that the disk 7 rotates in the arrow-marked direction to move the crank pin 8 to the neighborhood of the bottom dead center position such that the crimper 14 and the anvil 17 substantially perform the crimping work and, then, the crimper 14 provisionally comes to a stop at the crimping position. At this time, the crimper 14 is at rest (stop time t) showing a speed 0 while maintaining the state of pressurizing and pinching the barrel c of the terminal to continue the pressurizing action against the springback of the terminal barrel c, thus the load current reaching the peak value while showing a rising curve. Springback of said barrel c is prevented through this pressurizing and pinching action by this provisional halt.
After termial crimping, the servo motor 4 is caused to rotate the disk 7 in a direction reverse to the arrow-marked direction in the state shown in FIG. 10C such that the crimper 14 ascends to restore to the state (A).
In FIG. 11, the descending speed of the crimper 14 is sufficiently reduced from the speed thereof shown during the descent from the uppermost position to the terminal crimping start position. Therefore, such impact noise as is caused in a conventional flywheel type terminal crimping device will not be generated, thus contributing to noise prevention and job site improvement.
As data for determining whether the terminal crimping performance is good or not, the current value IU and IL as shown in FIG. 11B, are stored.
More specifically, FIG. 11B shows that I represents a standard value at the time of a normal step of crimping a given terminal and a given cable size, IU and IL represent a high limit and a low limit thereof, the high limit IU and the low limit IL being established by a preliminary test. If I is between IU and Ic, it means the normal crimping, in which the high limit IU and low limit Ic are established by the preliminary test.
As described in the foregoing, the crimping performance of the conventional terminal crimping device is determined by determining whether the value of electric current at the time of terminal crimping operation is in the preset range thereof. The determination by such a value of electric current alone is susceptible to a significant error to such an extent that values otherwise to be rejected can happen to be among those determined acceptable.